/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.connector.file.sink;

import org.apache.flink.api.common.RuntimeExecutionMode;
import org.apache.flink.api.common.restartstrategy.RestartStrategies;
import org.apache.flink.api.common.state.ListState;
import org.apache.flink.api.common.state.ListStateDescriptor;
import org.apache.flink.api.common.time.Time;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.configuration.ExecutionOptions;
import org.apache.flink.runtime.jobgraph.JobGraph;
import org.apache.flink.runtime.state.CheckpointListener;
import org.apache.flink.runtime.state.FunctionInitializationContext;
import org.apache.flink.runtime.state.FunctionSnapshotContext;
import org.apache.flink.streaming.api.CheckpointingMode;
import org.apache.flink.streaming.api.checkpoint.CheckpointedFunction;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.functions.source.RichParallelSourceFunction;
import org.apache.flink.streaming.api.graph.StreamGraph;

import org.junit.After;
import org.junit.Before;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;

import java.util.Collections;
import java.util.Map;
import java.util.UUID;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountDownLatch;

/**
 * Tests the functionality of the {@link FileSink} in STREAMING mode.
 */
@RunWith(Parameterized.class)
public class StreamingExecutionFileSinkITCase extends FileSinkITBase {

	private static final Map<String, CountDownLatch> LATCH_MAP = new ConcurrentHashMap<>();

	private String latchId;

	@Before
	public void setup() {
		this.latchId = UUID.randomUUID().toString();
		// We wait for two successful checkpoints in sources before shutting down. This ensures that
		// the sink can commit its data.
		// We need to keep a "static" latch here because all sources need to be kept running
		// while we're waiting for the required number of checkpoints. Otherwise, we would lock up
		// because we can only do checkpoints while all operators are running.
		LATCH_MAP.put(latchId, new CountDownLatch(NUM_SOURCES * 2));
	}

	@After
	public void teardown() {
		LATCH_MAP.remove(latchId);
	}

	/**
	 * Creating the testing job graph in streaming mode. The graph created is
	 * [Source] -> [File Sink]. The source would trigger failover if required.
	 */
	@Override
	protected JobGraph createJobGraph(String path) {
		StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
		Configuration config = new Configuration();
		config.set(ExecutionOptions.RUNTIME_MODE, RuntimeExecutionMode.STREAMING);
		env.configure(config, getClass().getClassLoader());

		env.enableCheckpointing(10, CheckpointingMode.EXACTLY_ONCE);

		if (triggerFailover) {
			env.setRestartStrategy(RestartStrategies.fixedDelayRestart(1, Time.milliseconds(100)));
		} else {
			env.setRestartStrategy(RestartStrategies.noRestart());
		}

		env.addSource(new StreamingExecutionTestSource(latchId, NUM_RECORDS, triggerFailover))
				.setParallelism(NUM_SOURCES)
				.sinkTo(createFileSink(path))
				.setParallelism(NUM_SINKS);

		StreamGraph streamGraph = env.getStreamGraph();
		return streamGraph.getJobGraph();
	}

	//------------------------ Streaming mode user functions ----------------------------------

	private static class StreamingExecutionTestSource extends RichParallelSourceFunction<Integer>
			implements CheckpointListener, CheckpointedFunction {

		private final String latchId;

		private final int numberOfRecords;

		/**
		 * Whether the test is executing in a scenario that induces a failover. This doesn't mean
		 * that this source induces the failover.
		 */
		private final boolean isFailoverScenario;

		private ListState<Integer> nextValueState;

		private int nextValue;

		private volatile boolean isCanceled;

		private volatile boolean snapshottedAfterAllRecordsOutput;

		private volatile boolean isWaitingCheckpointComplete;

		private volatile boolean hasCompletedCheckpoint;

		public StreamingExecutionTestSource(String latchId, int numberOfRecords, boolean isFailoverScenario) {
			this.latchId = latchId;
			this.numberOfRecords = numberOfRecords;
			this.isFailoverScenario = isFailoverScenario;
		}

		@Override
		public void initializeState(FunctionInitializationContext context) throws Exception {
			nextValueState = context.getOperatorStateStore().getListState(new ListStateDescriptor<>("nextValue", Integer.class));

			if (nextValueState.get() != null && nextValueState.get().iterator().hasNext()) {
				nextValue = nextValueState.get().iterator().next();
			}
		}

		@Override
		public void run(SourceContext<Integer> ctx) throws Exception {
			if (isFailoverScenario && getRuntimeContext().getAttemptNumber() == 0) {
				// In the first execution, we first send a part of record...
				sendRecordsUntil((int) (numberOfRecords * FAILOVER_RATIO * 0.5), ctx);

				// Wait till the first part of data is committed.
				while (!hasCompletedCheckpoint) {
					Thread.sleep(50);
				}

				// Then we write the second part of data...
				sendRecordsUntil((int) (numberOfRecords * FAILOVER_RATIO), ctx);

				// And then trigger the failover.
				if (getRuntimeContext().getIndexOfThisSubtask() == 0) {
					throw new RuntimeException("Designated Exception");
				} else {
					while (true) {
						Thread.sleep(50);
					}
				}
			} else {
				// If we are not going to trigger failover or we have already triggered failover, run until finished.
				sendRecordsUntil(numberOfRecords, ctx);

				// Wait the last checkpoint to commit all the pending records.
				isWaitingCheckpointComplete = true;
				CountDownLatch latch = LATCH_MAP.get(latchId);
				latch.await();
			}
		}

		private void sendRecordsUntil(int targetNumber, SourceContext<Integer> ctx) {
			while (!isCanceled && nextValue < targetNumber) {
				synchronized (ctx.getCheckpointLock()) {
					ctx.collect(nextValue++);
				}
			}
		}

		@Override
		public void snapshotState(FunctionSnapshotContext context) throws Exception {
			nextValueState.update(Collections.singletonList(nextValue));

			if (isWaitingCheckpointComplete) {
				snapshottedAfterAllRecordsOutput = true;
			}
		}

		@Override
		public void notifyCheckpointComplete(long checkpointId) throws Exception {
			if (isWaitingCheckpointComplete && snapshottedAfterAllRecordsOutput) {
				CountDownLatch latch = LATCH_MAP.get(latchId);
				latch.countDown();
			}

			hasCompletedCheckpoint = true;
		}

		@Override
		public void cancel() {
			isCanceled = true;
		}
	}
}
